1917] Studies on Coccobacillus Acridiorum D'Herelle 55 



From the results of the foregoing experiments it is clear 

 that Coccobacillus acridiorum is pathogenic to all the common 

 injurious locusts and grasshoppers of Eastern Canada, and that 

 these insects are equally susceptible. The immature stages of 

 the insects are more resistant than the adult stage. 



Infection does not spread readily to healthy insects by mere 

 contact with diseased locusts or other contaminated material. 

 The chief, if not the only method of spreading the disease, is by 

 ingestion of infected material. 



While many individuals are tolerant of a mild infection they 

 are not totally immune because all the locusts which survived 

 in the various experiments succumbed when re-inoculated with 

 a strong virulent culture. Their tolerance is probably due to 

 the presence of certain closely allied bacilli in the intestines. 



F. Experiments in the Field. 

 Experiments in an Enclosed Area: 



In order to be definitely certain of our results a small area 

 of a lawn was enclosed with screen-wire and numerous locusts 

 included in the enclosure. 



Experiment 1.- — The grass of the enclosed area was sprayed 

 with a bouillon culture of C. acridiorum and daily observations 

 made for a week. During this time not a single death was 

 recorded. The failure of this attempt was probably due to the 

 death of the organism as a result of its exposure to bright 

 sunlight. As it remained very bright for some time after this 

 the experiment was not repeated. 



Experiment 2. — A new portion of the lawn was enclosed and 

 sown with sweetened bran mash to which a bouillon culture of 

 the organism had been added. On the second day we found 21 

 dead locusts, and several others showing symptoms of the dis- 

 ease. At the end of five days we had collected altogether 108 

 dead locusts. Many of the survivors were then placed in insect 

 cages and the majority died within five days of their capture. 



Experiment 3. — Twenty locusts inoculated with a virulent 

 culture of C. acridiorum were introduced among the healthy 

 locusts in another enclosed area. At the end of the fifth day 

 only 39 dead locusts, including the inoculated ones, were found. 

 The experiment was continued for several days but no further 

 deaths were recorded. 



